let index = 0;
let stack = [];
function next() {
    let fn = stack[index];
    index++;
    if(typeof fn === 'function'){
        fn();
    }
}
function fn1() {
    console.log(1)
    next()
}
function fn2() {
    setTimeout(function() {
        console.log(2)
        next()
    },0)
   
}
function fn3() {
    console.log(3)
    next()
}

// stack.push(fn1)
// stack.push(fn2)
// stack.push(fn3)
function Man(name) {
    stack.push(function(){
        console.log(name);
        next();
    })
}
var p
function LazyMan(name) {
    p = new Man('Hank')
    return p;
}
Man.prototype.sleep = function(time){
    var that = this;
    
    stack.push(function(){
        setTimeout(function() {
            console.log(time + '秒')
            next()
            
        },time *1000)
    })
    return that;
}
Man.prototype.eat = function(food){
        
        stack.push(function(){
            console.log('eat '+food)
            next();
        })
        return this;
}
Man.prototype.sleepFirst = function(time){
    var that = this;
    stack.unshift(function(){
        setTimeout(function() {
            console.log('wake up after '+ time + '秒')
            next()

        },time *1000)
    })
    return that;
}

// LazyMan('Hank')

/* 输出:

Hi! This is Hank!

*/

// LazyMan('Hank').sleep(1).eat('dinner')

/* 输出:

Hi! This is Hank!

// 等待10秒..

Wake up after 10

Eat dinner~

*/

// LazyMan('Hank').eat('dinner').eat('“supper”')

/* 输出:

Hi This is Hank!

Eat dinner~

Eat supper~

*/

LazyMan('“Hank”').sleepFirst(2).eat('“supper”')

/* 等待5秒，输出

Wake up after 5

Hi This is Hank!

Eat supper

*/
// console.log(stack[0]())
next()